Biophysics-Group

The work of the Biophysics group comprises the investigation of the radiation environment in civil airflight altitudes, in low earth orbits, during interplanetary cruise and on planetary surfaces. Radiation exposures are determined using well characterised passive and active radiation detector systems. Passive detector packages as a minimum consists of plastic nuclear track detectors and thermoluminescence detectors, which allow mission integrated measurements of the absorbed dose, neutron dose, the heavy ion fluences and its spectral composition with respect to charge, energy and linear energy transfer (LET). Active systems in use are silicon detector telescopes or tissue equivalent proportional counters (TEPC), fro which flux of charged particles and the corresponding dose rate and LET spectra as a function of time are received. An important part of the work is the quantification of the detection efficiency of radiation detectors in reference fields. The group also develops, characterise and qualify new detector systems for the use as environmental dosemeters or as crew dosimeters for the International Space Station (ISS) or as new devices for missions to Mars. One recent development is the ESA facility MATROSHKA, which houses a human phantom equipped with a set of radiation detectors with the objective to assess organ doses for an astronaut working outside and inside the ISS.

A further task is the experimental and computational dosimetry of the radiation exposure at civil airflight altitudes. One part of this activity is the calculation and management of radiation exposure data for the Lufthansa aircrew. The expermental set for the measurements is comparable to that descibed above including the involvement of a human phantom.

Radiation is an acknowledged primary concern for manned spaceflight and is a potentially limiting factor for long term orbital and interplanetary missions. Results from numerous space probes demonstrate heightened radiation levels compared to the earth's surface and a change in the nature of the radiation field - particularly the presence of high energy heavy ions. Three sources of radiation are present.: solar cosmic rays, galactic cosmic rays and Radiation Belt particles.

In order to measure single components of the cosmic radiation field during single missions, different types of dosimeters have been developed and used. There two basic groups of dosimeters : active and passive dosimeters. The active type allows to measure online and provides exposure rates while the passive types deLiver an integral value. Both types are optimized to measure special radiation components and selected to complement each other in their recording characteristics.

MATROSHKA is an ESA project that is realized under the direction of the DLR in collaboration with industrial partners DTM technologies (Modena) and Kayser-Italia (Livorno). MATROSHKA is a facility that simulates as exact as possible an astronaut while he leaves the 'protective' area of the spaceship in order to carry out work in free space. The task is to measure particle fluence and energy spectra, dose and dose rates outside and inside a human phantom over the period of a year. The data are needed to improve the determination of radiation exposure of an astronaut performing a space walk.